Peroxyacid antimicrobail composition

ABSTRACT

A peroxyacid antimicrobial concentrate and use composition is provided comprising a C 5  peroxyacid in combination with a C 1  14 C 4  peroxyacid, a C 6  -C 18  peroxyacid, or mixtures thereof. The combination of these peracids produces a synergistic effect, providing a much more potent biocide than can be obtained by using these components separately. Other components can be added to the composition such as hydrotrope coupling agents, stabilizers, etc. An effective antimicrobial use solution is formed at low concentrations when the concentrate composition is diluted with water. Sanitizing of substantially fixed, &#34;in-place&#34; processing lines in dairies, breweries, and other food processing operations is one utility of the composition.

This is divisional application of Ser. No. 08/047,264, filed Apr. 12,1993, now U.S. Pat. No. 5,437,868 which is a continuation-in-partapplication of Ser. No. 07/734,580, filed on Jul. 23, 1991 now U.S. Pat.No. 5,200,189 which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to antimicrobial or biocidalcompositions. More particularly, the invention relates to peroxyacidantimicrobial concentrates and use solutions which can sanitizesurfaces, facilities and equipment found in food manufacture and foodprocessing and food service industries, and typically hard non-poroussurfaces in the health care industry.

BACKGROUND OF THE INVENTION

Antimicrobial compositions are particularly needed in the food andbeverage industries to clean and sanitize processing facilities such aspipelines, tanks, mixers, etc. and continuously operating homogenationor pasteurization apparatus. Sanitizing compositions have beenformulated in the past to combat microbial growth in such facilities.For example, Wang, U.S. Pat. No. 4,404,040, teaches a short chain fattyacid sanitizing composition comprising an aliphatic short chain fattyacid, a hydrotrope solubilizer capable of solubilizing the fatty acid inboth the concentrate and use solution, and a hydrotrope compatible acidso that the use solution has a pH in the range of 2.0 to 5.0.

Peroxy-containing compositions are known for use in the production ofmicrobicidal agents. One such composition is disclosed in Bowing et al.,U.S. Pat. No. 4,051,059 containing peracetic acid, acetic acid ormixtures of peracetic and acetic acid, hydrogen peroxide, anionicsurface active compounds such as sulfonates and sulfates, and water.

Peracetic acid, generally using some concentrations of acetic acid andhydrogen peroxide has been shown to be a good biocide, but only atfairly high concentrations (generally greater than 100 parts peraceticacid per million (ppm)). Similarly, peroxyfatty acids have also beenshown to be biocidal, but only at high concentrations (greater than 200ppm), such as in the composition disclosed in European PatentApplication No. 233,731. Peroxyacetic acid is a good biocide, but itpossesses a very strong odor, especially in the concentrate. For generaluse applications, for example, as a floor disinfectant or as anautomatic dish wash destainer or sanitizer, it is desirable to have aproduct with low odor. Thus, it is desirable to obtain a low odor peroxyantimicrobial formulation that is at least as effective as peroxyaceticacid.

Antimicrobial compositions having low use concentrations (less than 100ppm) which effectively kill microbes are particularly desirable. Lowconcentrations minimize use cost, surface corrosion, odor, carryover ofbiocide into foods and potential toxic effects to the user. Therefore, acontinuing need exists to provide such an antimicrobial composition foruse in food processing, food service and health care facilities. Incontrast to the prior art, the composition of the present invention hasthe unique advantage of having unanticipated excellent antimicrobial orbiocidal activity at low level use concentrations.

SUMMARY OF THE INVENTION

The invention includes a peroxyacid antimicrobial concentrate anddiluted end use composition comprising an effective biocidal amount ofeither a C₁ -C₄ peroxyacid, and an effective biocidal amount of a C₆-C₁₈ peroxyacid. The invention also includes a concentrate compositioncomprising the combination of an effective biocidal amount of a C₅peroxyacid with an effective biocidal amount of a C₁ -C₄ peroxyacid or aC₆ -C₈ peroxyacid. All three components of a C₁ -C₄ peroxyacid, C₅peroxyacid, and C₆ -C₁₈ peroxyacid can also be combined in thecomposition of the invention.

The above concentrate compositions can be diluted with a majorproportion of water to form antimicrobial sanitizing use solutionshaving a pH in the range of about 2 to 8. When a C₁ -C₄ peroxyacid isused, its concentration is at least about 10 ppm, preferably about 10 to75 ppm. When a C₅ peroxyacid is used, its concentration is at leastabout 10 ppm, preferably about 20 to 100 ppm. When a C₆ -C₁₈ peroxyacidis used, its concentration is at least about 1 ppm, preferably about 1to 25 ppm. Other components may be added such as a hydrotrope couplingagent for solubilizing the peroxyfatty acid in the concentrate form andwhen the concentrate composition is diluted with water.

In contrast to the prior art, we have discovered that at a low pH (e.g.preferably less-than 5), C₆ -C₁₈ peroxyacids such as peroxyfatty acidsare potent biocides at low levels. When used in combination with a C₁-C₄ peroxyacid such as peroxyacetic acid or a C₅ peroxyacid such asperoxyglutaric acid, a synergistic effect is obtained, providing a muchmore potent biocide than can be obtained by using these componentsseparately. This means that substantially lower concentrations ofbiocide can be used to obtain equal cidal effects, leading to lowercosts of the product and less potential for corrosion.

For example, we now have shown that combinations of peroxyglutaric acidand peroxyoctanoic acid possess surprisingly good bacterial killproperties at low concentrations, and both the use solution andconcentrated composition possess low odor. This composition can be madeby adding a mixture of glutaric acid and octanoic acid to a solution ofhydrogen peroxide in the presence of a stabilizer and a solubilizer. Wehave demonstrated, using ³ C NMR spectroscopy, that both peroxyacidsform in the above mixtures. That is, by merely adding the parentcarboxylic acids to a properly stabilized hydrogen peroxide system, theperoxyacids can be formed in sufficient quantity to give good bacterialkill at relatively low concentrations (e.g., about 50 ppm totalperoxyacids by titration). From antimicrobial testing, we know thatmixtures of peroxyglutaric acid and peroxyoctanoic acid are surprisinglyeffective, and that only small amounts of peroxyoctanoic acid are neededto greatly enhance the activity of a peroxyglutaric acid formula. Theresulting activity is greater than the arithematic sum of the activityof each material separately.

As the term is used herein, a C₆ -C₁₈ peroxyacid (or peracid) isintended to mean the product of the oxidation of a C₆ -C₁₈ acid such asa fatty acid, or a mixture of acids, to form a peroxyacid or mixture ofoxidized acids having from about 6 to 18 carbon atoms per molecule. Theterm C₁ -C₄ peroxyacid is intended to mean the product of the oxidationof a C₁ -C₄ carboxylic acid, or a mixture of acids thereof resulting ina single C₁₋₄ peroxyacids or a mixture of such peroxyacids. Thisincludes both simple and substituted C₁ -C₄ carboxylic acids. The termC₅ peroxyacid is intended to mean the product of the oxidation of a C₅carboxylic acid.

A method of sanitizing a surface, facilities or equipment comprises thesteps of contacting the surface, facilities or equipment with the usesolution made from the above concentrate compositions of the inventionat a temperature in the range of about 4° to 60° C. The composition isthen circulated or left in contact with the facilities or equipment fora time sufficient to sanitize, (generally at least 30 seconds) and thecomposition is thereafter drained or removed from the facilities orequipment.

One aspect of the invention are the novel, antimicrobial concentratecompositions which are capable of being diluted with a major proportionof water to form sanitizing use solutions. A further aspect of theinvention is the aqueous antimicrobial sanitizing use solutions whichare particularly suited,for "in-place" cleaning applications. Anotheraspect of the invention is a method of employing the use solutions inthe cleaning or sanitizing of various process facilities or equipment aswell as other surfaces.

DETAILED DESCRIPTION OF THE INVENTION

The invention resides in peroxyacid antimicrobial concentrate and usecompositions comprising various combinations of a C₅ peroxyacid, with aC₁ -C₄ peroxyacid, or a C₆ -C₁₈ peroxyacid. We have found that combiningthese acids produces an antimicrobial effect that is greater than thearithmatic sum of the activity of the individual acids, antimicrobialactivity, producing a much more potent biocide than can be obtained byusing these components separately. The concentrate compositions can bediluted with a major proportion of water to form antimicrobialsanitizing use solutions having a pH in the range of about 2 to 8. Thesanitizing use solutions can be used effectively to clean or sanitizefacilities and equipment used in the food processing, food service andhealth are industries.

Peracids

The present invention is based upon the surprising discovery that when aC₅ peroxy acid is combined with a C₆ -C₁₈ peroxyacid or a C₁ -C₄peroxyacid, a synergistic effect is produced and greatly enhancedantimicrobial activity is exhibited when compared to the C₅ peroxyacid,the C₆ -C₁₈ peroxyacid or the C₁ -C₄ peroxyacid alone. The presentcomposition blends can effectively kill microorganisms (e.g., a 5 log₁₀reduction in 30 seconds) at a concentration level below 100 ppm and aslow as 20 ppm of the peracid blend.

The preferred C₅ peroxyacid for use in the present invention isperoxyglutaric acid which is made from glutaric acid having the formulaCO₃ H(CH₂)₃ CO₃ H. The peroxyglutaric acid can be monoperoxy, diperoxyor mixtures of monoperoxy and diperoxy acids. Aqueous solutions ofperoxyglutaric acid containing an excess of hydrogen peroxide (H₂ O₂)and, if appropriate, also a stabilizer known for H₂ O₂ can be employedin the invention. Such solutions contain about 1 to 60 wt-% ofperoxyglutaric acid, about 1 to 50 wt-% of H₂ O₂, about 0 to 50 wt-% ofglutaric acid, and the remainder water. About 0.01 to 2 wt-% of astabilizer can be used such as urea or 2,3-pyridinedicarboxylic acidand/or 2,6-pyridinedicarboxylic acid. We have found that theseperoxyglutaric acid materials have surprising solubility in aqueoussystems and low odor.

A variety of C₆ C₁₈ peroxyacids may be employed in the composition ofthe invention such as peroxyfatty acids, monoperoxy- ordiperoxydicarboxylic acids, and peroxy aromatic acids. The C₆ -C₁₈peroxyacids employed in the present invention may be structurallyrepresented as follows: R₁ --CO₃ H, wherein R₁ is a hydrocarbon moietyhaving from about 5 to 17 carbon atoms (a C₈ peroxyacid is generallyrepresented structurally as C₇ --CO₃ H). R₁ may have substituents in thechain, e.g., --OH, CO₂ H, or heteroatoms (e.g., --O-- as in alkylethercarboxylic acids), as long the antimicrobial properties of the overallcomposition are not significantly affected. The "R₁ " substituents orheteroatoms may change the overall acidity (i.e., pKa) of the carboxylicacids herein described. Such modification is within the contemplation ofthe present invention provided the advantageous antimicrobialperformance is maintained. Furthermore, R₁ may be linear, branched,cyclic or aromatic. Preferred hydrocarbon moieties (i.e. preferred R₁'s) include linear, saturated, hydrocarbon aliphatic moieties havingfrom 7 to 11 carbon atoms (or 8 to 12 carbon atoms per molecule).

Specific examples of suitable C₆ -C₁₈ carboxylic fatty acids which canbe reacted with hydrogen peroxide to form peroxyfatty acids include suchsaturated fatty acids as hexanoic (C₆), enanthic (heptanoic) (C₇),caprylic (octanoic) (C₈), perlargonic (nonanoic) (C₉), capric (decanoic)(C₁₀), undecyclic (undecanoic) (C₁₁), lauric (dodecanoic) (C₁₂),trideclic (tridecanoic) (C₁₃), myristic (tetradecanoic) (C₁₄), palmitic(hexadecanoic) (C₁₆), and stearic (octodecanoic) (C₁₈). These acids canbe derived from both natural and synthetic sources. Natural sourcesinclude animal and vegetable fats or oils which should be fullyhydrogenated. Synthetic acids can be produced by the oxidation ofpetroleum wax. Particularly preferred peroxyfatty acids for use in thecomposition of the invention are linear-monoperoxy aliphatic fatty acidssuch as peroxyoctanoic acid, peroxydecanoic acid, or mixtures thereof.

Other suitable C₆ -C₁₈ peroxyacids are derived from the oxidation ofdicarboxylic acids and aromatic acids. Suitable dicarboxylic acidsinclude adipic acid (C₆) and sebacic acid (C₁₀). Examples of a suitablearomatic acid include benzoic acid, phthalic acid, terephthalic acid,hydroxy benzoic acid, etc. These acids can be reacted with hydrogenperoxide to form the peracid form suitable for use in the composition ofthe invention. Preferred peracids in this group include monoperoxy- ordiperoxyadipic acid, monoperoxy- or diperoxysebacic acid, andperoxybenzoic acid.

The C₁ -C₄ peroxyacid component can be derived from a C₁ -C₄ carboxylicacid or dicarboxylic acid by reacting the acid with hydrogen peroxide.Examples of suitable C₁ -C₄ carboxylic acids include acetic acid,propionic acid, glycolic acid, and succinic acid. Preferable C₁ -C₄peroxycarboxylic acids for use in the composition of the inventioninclude peroxyacetic acid, peroxypropionic acid, peroxyglycolic acid,peroxysuccinic acid, or mixtures thereof.

The above peroxyacids provide antibacterial activity against a widevariety of microorganisms, such as gram positive (e.g., Staphylococcusaureus) and gram negative (e.g., Escherichia coli) microorganisms,yeast, molds, bacterial spores, etc. When combined, the aboveperoxyacids have greatly enhanced activity compared to a C₁ -C₄peroxyacid, a C₅ peroxyacid, or a C₆ -C₁₈ peroxyacid alone.

The antimicrobial concentrates of the present invention can compriseabout 0 to 10 wt-%, preferably about 0.05 to 5 wt-%, and most preferablyabout 0.1 to 2 wt-% of a C₆ -C₁₈ peroxyacid; about 0 to 30 wt-%,preferably about 1 to 25 wt-%, and most preferably about 5 to 20 wt-% ofa C₅ peroxyacid; and about 0 to 25 wt-%, preferably about 0.5 to 20wt-%, and most preferably about 1 to 15 wt-% of a C₁ -C₄ peroxyacid. Oneconcentrate composition preferably has a weight ratio of C₁ -C₄peroxyacid to C₆ -C₁₈ peroxyacid of about 15:1 to 3:1. Anotherconcentrate composition preferably has a weight ratio of C₅ peroxyacidto C₆ -C₁₈ peroxyacid of about 20:1 to 2:1. A further concentratecomposition has a weight ratio of C₅ peroxyacid to C₁ -C₄ peroxyacid ofabout 10:1 to 1:10. The concentrate compositions contain sufficient acidso that the end use solution has a pH of about 2 to 8, preferably about3 to 7. Some acidity may come from an inert acidulant which may beoptionally added (e.g., phosphoric acid).

The peracid components used in the composition of the invention can beproduced in a simple manner by mixing a hydrogen peroxide (H₂ O₂)solution with the desired amount of carboxylic acid or acid blend. Withthe higher molecular weight fatty acids, a hydrotrope coupler may berequired to fully solubilize the fatty acid. The H₂ O₂ solution also canbe added to previously made peroxyacids such as peroxyacetic acid,peroxyglutaric acid or various peroxy fatty acids to produce theperoxyacid composition of the invention. The concentrates can containabout 1 to 50 wt-%, preferably about 5 to 25 wt-% of hydrogen peroxide.

The concentrate compositions can further comprise a free C₆ -C₁₈carboxylic acid, a free C₅ carboxylic acid, a free C₁ -C₄ carboxylicacid, or mixtures thereof. The free acids will preferably correspond tothe starting materials used in the preparation of the peroxyacidcomponents. The free C₆ -C₁₈ carboxylic acid is preferably linear andsaturated, has 8 to 12 carbon atoms per molecule, and can also comprisea mixture of acids. The free C₆ -C₁₈ carboxylic acid, free C₅ carboxylicacid, and free C₁ -C₄ carboxylic acid can be present as a result of anequilibrium reaction with the hydrogen peroxide to form the peroxyacids.

Optional Components

Various optional materials may be added to the composition of theinvention to help solubilize the fatty acids, restrict or enhance theformation of foam, to control hard water, to stabilize the composition,or to further enhance the antimicrobial activity of the composition.

The compositions of the invention can contain a surfactant hydrotropecoupling agent or solubilizer that permits blending both fatty acids andshort chain perfatty acids in aqueous liquids. Functionally speaking,the suitable couplers which can be employed are non-toxic and retain thefatty acid and the perfatty acid in aqueous solution throughout thetemperature range and concentration to which a concentrate or any usesolution is exposed.

Any hydrotrope coupler maybe used provided it does not react withthe-other components of the composition or negatively affect theantimicrobial properties of the composition. Representative classes ofhydrotropic coupling agents or solubilizers which can be employedinclude anionic surfactants such as alkyl sulfates and alkanesulfonates, linear alkyl benzene or naphthalene sulfonates, secondaryalkane sulfonates, alkyl ether sulfates or sulfonates, alkyl phosphatesor phosphonates, dialkyl sulfosuccinic acid esters, sugar esters (e.g.,sorbitan esters) and C₈ -C₁₀ alkyl glucosides. Preferred coupling agentsfor use in the present invention include n-octanesulfonate, available asNAS 8D from Ecolab, and the commonly available aromatic sulfonates suchas the alkyl benzene sulfonates (e.g. xylene sulfonates) or naphthalenesulfonates.

Some of the above hydrotropic coupling agents independently exhibitantimicrobial activity at low pH. This adds to the efficacy of thepresent invention, but is not the primary criterion used in selecting anappropriate coupling agent. Since it is the presence of perfatty acid inthe protonated neutral state which provides biocidal activity, thecoupling agent should be selected not for its independent antimicrobialactivity but for its ability to provide effective interaction betweenthe substantially insoluble perfatty acids described herein and themicroorganisms which the present compositions control.

The hydrotrope coupling agent can comprise about 0.1 to 30 wt-%,preferably about 1 to 20 wt-%, and most preferably about 2 to 15 wt-% ofthe concentrate composition.

Compounds such as mono, di and trialkyl phosphate esters may be added tothe composition to suppress foam. Such phosphate esters would generallybe produced from aliphatic linear alcohols, there being from 8 to 12carbon atoms in the aliphatic portions of the alkyl phosphate esters.Alkyl phosphate esters possess some antimicrobial activity in their ownright under the conditions of the present invention. This antimicrobialactivity also tends to add to the overall antimicrobial activity of thepresent compositions even though the phosphate esters may be added forother reasons. Furthermore, the addition of nonionic surfactants wouldtend to reduce foam formation herein. Such materials tend to enhanceperformance of the other components of the composition, particularly incold or soft water. A particularly useful nonionic surfactant for use asa defoamer is nonylphenol having an average of 12 moles of ethyleneoxide condensed thereon, it being encapped with a hydrophobic portioncomprising an average of 30 moles of propylene oxide.

A variety of chelating agents can be added to the composition of theinvention to enhance biological activity, cleaning performance andstability of the peroxyacids. For example,1-hydroxyethylidene-1,1-diphosphonic acid commercially available fromthe Monsanto Company under the designation "DEQUEST 2010" has been foundto be effective. Other effective chelating agents include 1,6 pyridinedicarboxylic acid. Chelating agents can be added to the presentcomposition to control or sequester hardness ions such as calcium andmagnesium. In this manner both detergency and sanitization capabilitycan be enhanced.

Other materials which are sufficiently stable at the low pH contemplatedby the present composition may be added to the composition to impartdesirable qualities depending upon the intended ultimate use. Forexample, phosphoric acid (H₃ PO₄) can be added to the composition of theinvention. Additional compounds can be added to the concentrate (andthus ultimately to the use solution) to change its color or odor, toadjust its viscosity, to enhance its thermal (i.e., freeze-thaw)stability or to provide other qualities which tend to make it moremarketable.

The compositions of the invention can be made by combining by simplemixing at least two of a C₆ -C₁₈ peroxyacid, a C₁ -C₄ peroxyacid, and aC₅ peroxyacid. These compositions could be formulated with preformedperoxyacids. A preferred composition of the invention can be made bymixing a C₅ carboxylic acid with a C₁ -C₄ carboxylic acid or analiphatic C₆ -C₁₈ carboxylic acid, optionally a coupler and/or astabilizer, and reacting this mixture with hydrogen peroxide. A stableequilibrium mixture is produced containing a C₅ peroxyacid and a C₁ -C₄peroxyacid or an aliphatic C₆ -C₁₈ peroxyacid by allowing the mixture tostand for from one to seven days at 15° C. to 25° C. As with any aqueousreaction of hydrogen peroxide with a free carboxylic acid, this gives atrue equilibrium mixture. In this case, the equilibrium mixture willcontain hydrogen peroxide, an unoxidized C₅ carboxylic acid, anunoxidized C₁ -C₄ carboxylic acid or an unoxidized aliphatic C₆ -C₁₈carboxylic acid, a C₅ peroxyacid, a C₁ -C₄ peroxyacid or an aliphatic C₆-C₁₈ peroxyacid, and optionally various couplers and/or stabilizers.

By using the above approach, the compositions of the invention can beformulated by merely mixing readily available raw materials, e.g.,glutaric acid, acetic acid, hydrogen peroxide and fatty acid. Byallowing solution time for equilibrium to be obtained, the productcontaining the active biocides is obtained. In varying the ratio of C₅carboxylic acid to C₁ -C₄ carboxylic acid or C₆ -C₁₈ carboxylic acid, itis easy to vary the ratio of C₅ peroxyacid to C₁ -C₄ peroxycarboxylicacid or C₆ -C₁₈ peroxyacid.

Concentrate and Use Compositions

The present invention contemplates a concentrate composition which isdiluted to a use solution prior to its utilization as a sanitizer.Primarily for reasons of economics, the concentrate would normally bemarketed and the end user would dilute the concentrate with water to ause solution. Preferred antimicrobial concentrate compositions compriseabout 1 to 25 wt-%, preferably about 5 to 20 wt-%, of a C₅ peroxyacid,about 0.01 to 10 wt-%, preferably about 0.05 to 5 wt-%, of a C₆ -C₁₈peroxyfatty acid, and/or about 0.1 to 25 wt-%, preferably about 0.5 to20 wt-%, of a C₁ -C₄ peroxyacid. The concentrate compositions canfurther include about 0.1 to 30 wt-% of a hydrotrope coupling agent, andabout 1 to 50 wt-% of hydrogen peroxide. Other acidulants may optionallybe employed in the compositions such as phosphoric acid. All three ofthe above peroxyacids may be combined together in the above amounts toform an effective antimicrobial concentrate composition.

The level of active components in the concentrate composition isdependent upon the intended dilution factor and desired acidity in theuse solution. The C₆ -C₁₈ peroxyacid component is generally obtained byreacting a C₆ -C₁₈ carboxylic acid with hydrogen peroxide in thepresence of a C₁ -C₄ carboxylic acid and/or a C₅ carboxylic acid. Theresulting concentrate is diluted with water to provide the use solution.Generally, a dilution of 1 fluid oz. to 4 gallons (i.e. dilution of 1 to500 by volume) or to 8 gallons (i.e. dilution of 1 to 1,000 by volume)of water can be Obtained with 2% to 20% total peracids in theconcentrate. Higher use dilution can be employed if elevated usetemperature (greater than 20° C.) or extended exposure time (greaterthan 30 seconds) are also employed.

In its intended end use, the concentrate is diluted with a majorproportion of water and used for purposes of sanitization. The typicalconcentrate composition described above is diluted with available tap orservice water to a formulation of approximately 1 oz. concentrate to 8gallons of water. Aqueous antimicrobial sanitizing use solutions cancomprise at least about 1 part per million (ppm), preferably about 10 to100 ppm, of a C₅ peroxyacid, at least about 1 ppm, preferably about 2 to10 ppm of a C₆ -C₁₈ peroxyacid, and/or at least about 10 ppm, preferablyabout 20 to 50 ppm of a C₁ -C₄ peroxyacid. Any two of the above peracidsmay be present in the use solution or all three may be present,depending on the concentrate composition ingredients. In a preferredcomposition, the weight ratio of C₆ -C₁₈ peroxyacid to C₅ peroxyacidranges from about 0.01 to 0.5 parts, preferably about 0.02 to 0.2 parts,of C₆ -C₁₈ peroxyacid per part of C₅ peroxyacid. Preferably the totalperacid concentration in the use solution is less than about 75 ppm, andmost preferably between about 5 to 50 ppm. Higher levels of peracids canbe employed in the use solution to obtain disinfecting or sterilizingresults.

The aqueous use solution can further comprise at least about 1 ppm,preferably about2 to 20 ppm, of a hydrotrope coupling agent, and atleast about 1 ppm, preferably about 2 to 200 ppm of hydrogen peroxide.The use solution can also comprise at least about 1 ppm, preferablyabout 2 to 200 ppm of a free C₆ -C₁₈ carboxylic acid, a free C₅carboxylic acid, a free C₁ -C₄ carboxylic acid, or mixtures thereof. Theaqueous use solutions have a pH in the range of about 2 to 8, preferablyabout 3 to 7.

Methods of Use

As noted above, the present composition is useful in the cleaning orsanitizing of processing facilities or equipment in the food service,food processing or health care industries. Examples of processfacilities in which the composition of the invention can be employedinclude a dairy milk line, a continuous brewing system, food processinglines such as pumpable food systems and beverage lines, etc. Foodservice wares can also be sanitized with the composition of theinvention. The composition is also useful in sanitizing or disinfectingsolid surfaces such as floors, counters, furniture, medical tools andequipment, etc., found in the health care industry. Such surfaces oftenbecome contaminated with liquid body spills such as blood, otherhazardous body fluids or mixtures thereof.

Generally, the actual cleaning of the in-place system or other surface(i.e., removal of unwanted offal therein) is accomplished with adifferent material such as a formulated detergent which is introducedwith heated water. After this cleaning step, the instant sanitizingcomposition would be applied or introduced into the system at a usesolution concentration in unheated, ambient temperature water. Thepresent sanitizing composition is found to remain in solution in cold(e.g., 40° F./4° C.) water and heated (e.g., 140° F./60° C.) water.Although it is not normally necessary to heat the aqueous use solutionof the present composition, under some circumstances heating may bedesirable to further enhance its antimicrobial activity.

A method of sanitizing substantially fixed in-place process facilitiescomprises the following steps. The use solution composition of theinvention is introduced into the process facilities at a temperature inthe range of about 4° to 60° C. After introduction, the use solution iscirculated throughout the system for a time sufficient to sanitize theprocess facilities (i.e., to kill undesirable microorganisms). After thesystem has been sanitized by means of the use solution composition, theuse solution is drained from the system. Upon completion of thesanitizing step, the system optionally may be rinsed with othermaterials such as potable water. The composition is preferablycirculated through the process facilities for 10 minutes or less andallowed to drain without further treatment.

The composition may also be employed by dipping food processingequipment into the use solution, soaking the equipment for a timesufficient to sanitize the equipment, and draining excess solution offthe equipment. The composition may be further employed by spraying orwiping food processing surfaces with the use solution, keeping thesurfaces wet for a time sufficient to sanitize the surfaces, andremoving excess solution by draining vertically, vacuuming, etc.

The composition of the invention may also be used in a method ofsanitizing hard surfaces such as institutional type equipment, utensils,dishes, health care equipment or tools, and other hard surfaces. Thecomposition may also be employed in sanitizing clothing items or fabricwhich has become contaminated. The composition is contacted with any ofthe above contaminated surfaces or items at use temperatures in therange of about 4° to 60° C., for a period of time effective to sanitize,disinfect, or sterilize the surface or item. For example, theconcentrate composition can be injected into the wash or rinse water ofa laundry machine and contacted with contaminated fabric for a timesufficient to sanitize the fabric. Excess solution can then be removedby rinsing or centrifuging the fabric.

As the term "sanitizing" is used in the method of the instant invention,it means a reduction in the population numbers of undesirablemicroorganisms by about 5 powers of 10 or greater (i.e., at least 5orders of magnitude) after a 30 second exposure time. It is to beemphasized that the instant use solution provides cleaning as well assanitizing performance although its primary utility is sanitizing. Thecomposition may also be used to achieve disinfection or sterilization(i.e., elimination of all microorganisms) by employing higher levels ofperacids in the use solution.

The following Examples which contain a best mode, are intended toillustrate the above invention and should not be construed as to narrowits scope. One skilled in the art will readily recognize that theseExamples suggest many other ways in which the present invention could bepracticed. Examples 1-14 demonstrate cooperation between C₁₋₄ peracidsand C₆₋₈ peracids. Examples 15 and 16 demonstrate the superiority of aC₅ peracid in combination with either a C₁₋₄ peracid, or a C₆₋₈ peracid.Examples 17-32 demonstrate the efficacy of the blends preparativeinformation, stability, and aging tests.

EXAMPLE 1

Experiments were conducted to determine the antimicrobial efficacy ofpure peroxyacids. Table I below demonstrates the antimicrobial efficacyof pure peroxyacids at very low levels when exposed to S. aureus and E.coli. The peroxyacids listed in Table I were tested by diluting them in0.05M citrate buffer made in distilled water and were exposed to thebacteria for 30 seconds at 20° C. As Table I indicates, thediperoxyacids were somewhat less active than the peroxyfatty acids.Peroxydecanoic acid was very effective at very low levels against S.aureus, but higher levels were required to be effective against E. coli.Higher levels were also required at pH 5.

                  TABLE I                                                         ______________________________________                                        Comparison of Cidal Activity of Peroxyacids                                                 Minimum concentration required                                                for 5 log reduction (ppm).sup.(a)                               Peroxyacid  pH      S. aureus   E. coli                                       ______________________________________                                        Peroxyhexanoic                                                                            3.5     15          15                                            (C.sub.6)   5.0     20          15                                            Diperoxyadipic                                                                            3.5     >50         40                                            (C.sub.6)   5.0     >60         35                                            Peroxyoctanoic                                                                            3.5      5           5                                            (C.sub.8)   5.0     10          15                                            Peroxydecanoic                                                                            3.5      3          10                                            (C.sub.10)  5.0      1          30                                            Diperoxysebacic                                                                           3.5     15          15                                            (C.sub.10)  5.0     10          50                                            ______________________________________                                         .sup.(a) Peroxyacids tested at 5ppm increments, or at 1, 3, and 5 ppm         where appropriate.                                                       

In Table II below, the degree of antimicrobial kill resulting from acooperation between the C₂ and C₃ peroxyacids when combined with C₈ andC₁₀ peroxyfatty acids is shown. As Table II shows, there was little orno antimicrobial activity when the C₂ and C₃ peroxyacids and the C₈ andC₁₀ peroxyfatty acids were tested alone. However, when a C₂ or C₃peroxyacid was combined with a C₈ or C₁₀ peroxyfatty acid, the bacterialkill of E. coli surprisingly increased. These tests were conducted at pH4.5 or 5 (see Table II).

                  TABLE II                                                        ______________________________________                                        Cooperative Interaction of Peroxyacids                                        C.sub.2                                                                              C.sub.3   C.sub.8                                                      [Peroxy-                                                                             [Peroxy-  [Peroxy- C.sub.10   Microbial                                acetic]                                                                              propionic]                                                                              octanoic]                                                                              [Peroxydecanoic]                                                                         Population                               (ppm)  (ppm)     (ppm)    reduction (ppm)                                                                          Log Reduc.                               ______________________________________                                        25               0                   0.sup.a                                   0               5                   0.1.sup.a                                25               5                   3.8.sup.a                                       25        0                   0.3.sup.b                                        0        6                   0.1.sup.b                                       25        6                   3.9.sup.b                                30                        0          0.7.sup.a                                 0                        6          0.sup.a                                  30                        6          2.6.sup.a                                ______________________________________                                         .sup.a E. coli pH 5, distilled water                                          .sup.b E. coli, pH 4.5, 500 ppm hard water                               

EXAMPLES 2-6

A two-component system containing peracetic acid and perfatty acid wasformulated and tested to determine its sanitizing activity over just aperacetic acid system. Table III shows premixes 1 and 2 used in makingthe composition. The premixes were both made with H₂ O₂ (35% solution),acetic acid, Dequest 2010, and with/without H₃ PO₄. Premix 1 was madeabout 5 months before premix 2. To each premix was added NAS 8D, a C₈fatty acid or Emery 658 as shown in Table IV to complete the formulationof Examples 2-5. Example 6 was formulated as a control and had no fattyacid.

                  TABLE III                                                       ______________________________________                                        Peracid Premixes                                                                             Wt-% Component                                                 Component        Premix 1 Premix 2                                            ______________________________________                                        H.sub.2 O.sub.2 (35%)                                                                          75.0     35.0                                                Acetic acid (glacial)                                                                          24.0     35.0                                                Dequest 2010     1.0      1.0                                                 H.sub.3 PO.sub.4 (85%)                                                                         --       29.0                                                ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                        Perfatty Acid/Peracetic Acid Formulations                                              Wt-% Ingredient                                                      Ingredient Ex. 2    Ex. 3  Ex. 4  Ex. 5                                                                              Ex. 6                                  ______________________________________                                        Premix 1   80.0     --     80.0   --   --                                     Premix 2   --       80.0   --     80.0 --                                     NAS 8D     10.0     10.0   10.0   10.0 --                                     C.sub.8 Fatty Acid                                                                       10.0     10.0   --     --   --                                     Emery 658  --       --     10.0   10.0 --                                     Acetic Acid                                                                              --       --     --     --   24.0                                   (Glacial)                                                                     H.sub.2 O.sub.2 (35%)                                                                    --       --     --     --   75.0                                   Dequest 2010                                                                             --       --     --     --    1.0                                   ______________________________________                                    

Table V shows the sanitizing activity measured from each formulation ofExamples 2-5 at 50, 100, or 150 ppm peracetic acid against S. aureus(Example 6 is a control).

                  TABLE V                                                         ______________________________________                                        Sanitizing Efficacy of Perfatty Acid/                                         Peracetic Acid System vs.                                                     Sanitizing Efficacy of Peracetic Acid System                                        Total    Fatty    Test                                                  Ex-   Peracid.sup.(a)                                                                        Acid     Concentration.sup.(a)                                                                   Test Log.sup.(b)                            ample (Percent)                                                                              (Percent)                                                                              (ppm)     pH   Reduction                              ______________________________________                                        2     7.69     10.0     150       3.53 >7.06                                                          100       3.64 >7.06                                                           50       3.83 >7.06                                  3     11.21    10.0     150       2.71 >7.06                                                          100       2.80 >7.06                                                           50       3.08 >7.06                                  4     9.08     10.0     150       3.64 >7.06                                                          100       3.65 >7.06                                                           50       3.85 >7.06                                  5     10.92    10.0     150       2.68 >7.06                                                          100       2.77 >7.06                                                           50       3.10 >7.06                                  6     10.40    --       150       3.56 >7.06                                                          100       3.68  3.89                                                           50       3.93 NMA.sup.(c)                            ______________________________________                                         .sup.(a) As peracetic acid                                                    .sup.(b) Average of duplicate testing against S. aureus.                      .sup.(c) No measurable activity.                                         

Extremely good kill (>7 log reduction) was obtained with or without H₃PO₄ in the perfatty acid formulations of Examples 2-6. The two componentsystem of C₈ fatty acid or Emery 658 in combination with peracetic acid(Example 2-5) had significantly better kill than the peracetic acidsystem alone (Example 6) at a test concentration of 50 to 100 ppm. Noactivity was measured at 50 ppm with the single peracetic acid system ofExample 6.

EXAMPLE 7-10

The effect of alkyl chain length on antimicrobial efficacy of perfattyacids was determined for percaprylic (C₈) acid, percapric (C₁₀) acid anda percaprylic/percapric (3:1) perfatty acid mixture using thecompositions of Examples 7-8 summarized in Table VI below.

                  TABLE VI                                                        ______________________________________                                                    Wt-% of Ingredient                                                Ingredient    Ex. 7  Ex. 8     Ex. 9                                                                              Ex. 10                                    ______________________________________                                        Percaprylic    1     --        --   --                                        (C.sub.8) Acid                                                                Percapric     --      1        --   --                                        (C.sub.10) Acid                                                               C.sub.8 + C.sub.10 (3:1)                                                                    --     --         1   --                                        Perfatty Acid                                                                 Acetic Acid   10     10        10   10                                        Water         84     84        84   85                                        NAS 8D         5      5         5    5                                        ______________________________________                                    

The antimicrobial efficacy of Examples 7-10 are summarized in Table VIIbelow. Examples 7-9 were tested using three samples (a, b, c) of 5, 10,and 15 ppm of perfatty acid respectively. Example 10, containing noperfatty acid, was diluted to an equivalent formulation of Examples 7-9containing perfatty acid. As can be seen from Table VII, significantkill occurred at 5 ppm for S. aureus using Examples 7-9. Significantkill occurred against E. coli at 10 ppm of perfatty acid in Examples7-9. Example 10 (having no perfatty acid) did not produce any kill ofeither microorganism.

                  TABLE VII                                                       ______________________________________                                        Antimicrobial Efficacy of Examples 7-10                                                        Perfatty Acid                                                                 Concentration                                                                             Log Kill                                         Example Sample   (ppm)       S. aureus                                                                             E. coli                                  ______________________________________                                        7       a        5           >7.0    3.6                                              b        10          --      >7.2                                             c        15          --      >7.2                                     8       a         5          >7.0    3.0                                              b        10          --      >7.2                                             c        15          --      >7.2                                     9       a         5          >7.0    <3.0                                             b        10          --      >7.2, 5.5                                        c        15          --      >7.2                                     10      a        --.sup.a    0       --                                               b        --.sup.b    --      0                                        ______________________________________                                         .sup.a Equivalent total product concentration as Examples 7, 8, 9 at 5 pp     perfatty acid.                                                                .sup.b Equivalent total product concentration as Examples 7, 8, 9 at 15       ppm perfatty acid.                                                       

EXAMPLE 11

The antimicrobial activity of percaprylic acid against E. coli wasmeasured at a 30 second exposure at varying pH's. The formulationcontained 94% water, 5% NAS 8D, and 1% percaprylic acid. The formulationwas diluted in a buffer of 0.05M citrate and 0.05M potassium phosphate.The log kill of this formulation at increasing pH's is summarized inTable VIII. Samples containing 7 ppm and 25 ppm of percaprylic acid weretested. As Table VIII indicates, significant kill at 7 ppm occurred at apH of 3.0. Significant kill levels were maintained at 25 ppm through apH of 7.0.

                  TABLE VIII                                                      ______________________________________                                        Antimicrobial Efficacy of                                                     Percaprylic Acid against E. coli                                                     Log Kill (Perfatty                                                                           Log Kill (Perfatty                                      pH     Concentration 7 ppm)                                                                         Concentration 25 ppm)                                   ______________________________________                                        3.0    >7.2           >7.2                                                    5.0    <3.0           >7.2                                                    7.0    <3.0           >7.2                                                    8.9    --             <3.0                                                    9.0    <3.0           --                                                      ______________________________________                                    

EXAMPLES 12-14

The compositions of Examples 12-14 were made to determine thelimitations on cidal activity of compositions containing at least 30%acetic acid. Higher acetic acid formulations were also tested for theircidal activity. The composition of Example 14 was prepared with nocoupler (NAS 8D). The compositional ingredients of Examples 12-14 aresummarized below in Table IX.

                  TABLE IX                                                        ______________________________________                                                    Wt-% of Ingredient                                                Ingredient    Example 12                                                                              Example 13 Example 14                                 ______________________________________                                        Acetic Acid   30.0      50.0       50.0                                       H.sub.2 O.sub.2 (35%)                                                                       30.0      15.0       15.0                                       Dequest 2010   1.0       1.0        1.0                                       C.sub.8 Fatty Acid                                                                           4.0       6.0        5.0                                       NAS 8D (Spray Dried)                                                                         5.0       5.0       --                                         Distilled Water                                                                             30.0      23.0       29.0                                       ______________________________________                                    

The antimicrobial efficacy of Examples 12-14 was determined using theprocedure of the standard A.O.A.C. sanitizing test. The compositions ofExamples 12-14 were diluted with 500 ppm hard water and employed at 25°C. The bacteria used in the test procedure were S. aureus and E. coli,and TGE plating medium was employed. Exposure time of the compositionsto the bacteria was 30 seconds. The neutralizer employed in the testingprocedure contained 0.1% thiosulfate, 1.0% peptone, and 0.025% catalase.The antimicrobial activity of Examples 12-14 is summarized in Table Xbelow.

                  TABLE X                                                         ______________________________________                                        Cidal Activity of Examples 12-14                                                                   Log Reduction                                            Formulation                                                                             Concentration                                                                              pH      S. aureus                                                                            E. coli                                 ______________________________________                                        Example 12                                                                              1 oz:8 gal..sup.a                                                                          4.48    >7.15  >6.89                                             1 oz:10 gal.sup.b                                                                          4.83    >7.15  >6.89                                             1 oz:12 gal..sup.c                                                                         5.04    >7.15  6.41                                              1 oz:14 gal..sup.d                                                                         5.52    >7.15  5.76                                              1 oz:16 gal..sup.e                                                                         5.94    >7.15  2.95                                    Example 13                                                                              40 ppm Active                                                                              4.16    >7.15  >6.89                                   Example 14                                                                              40 ppm Active                                                                              4.04    >7.15  >6.89                                   ______________________________________                                         .sup.a 54.2 ppm peracid                                                       .sup.b 43.3 ppm peracid                                                       .sup.c 36.1 ppm peracid                                                       .sup.d 31.0 ppm peracid                                                       .sup.e 27.2 ppm peracid                                                  

As Table X indicates, very low concentrations of combinations ofperoxyacetic acid and peroxyfatty acid are very effective in killingbacteria. Also, Example 14 showed that the composition of the inventionis antimicrobially effective without a hydrotrope coupler.

EXAMPLE 15

Samples 1-10 were prepared to test the cidal activity of C₂, C₅, and C₈peroxyacids, both alone and in various combinations. The peroxyacetic(C₂) acid was a production sample made by Ecolab Inc. under the tradename of Oxonia P3. Iodometric and ceric sulfate titrations on the day ofmicrobiological testing gave a peroxyacetic acid concentration of 6.04%.The peroxyglutaric (C₅) acid was prepared by mixing 84 g of 35% hydrogenperoxide with 1 g of Dequest 2010 (Monsanto Corporation) and 15 g ofglutaric acid. After standing for one week, the concentration ofperoxyglutaric acid (by titration) had reached equilibrium. Titration onthe day of microbiological testing gave a peroxyglutaric acidconcentration of 11.42%. The peroxyoctanoic (C₈) acid was prepared bythe method of W. E. Parker, C. Ricciuti, C. L. Ogg and D. Swern, J. Am.Chem. Soc. 77 4037 (1955), incorporated herein by reference. Severalrecrystallizations from low boiling petroleum ether gave the pureperoxyoctanoic acid. Titration on the day of microbiological testingshowed the crystalline peroxyoctanoic acid to be 98-100% pure.

Microbiological test sample solutions were then made from each of theabove peroxyacids. The Oxonia P3 (6.04% peroxyacetic acid) was firstdiluted 1:10 to obtain a working solution containing 6040 ppm ofperoxyacetic acid. To obtain a 25 ppm use solution, 1.035 ml of thisworking solution was diluted to 250 ml with deionized water. To obtaina50 ppm use solution, 2.07 ml of the working solution was similarlydiluted to 250 ml. The peroxyglutaric acid (11.42% titratableperoxyglutaric acid) was diluted 1:20 with deionized water to obtain a5710 ppm working solution of peroxyglutaric acid. To obtain a 25 ppm anda 50 ppm use solution, 1.095 ml an 2.189 ml were each diluted to 250 mlwith deionized water. A solution of peroxyoctanoic acid was prepared bymixing 9.4144 g of deionized water with 0.5021 g of sodium octanesulfonate (a non-active coupler) and 0.1017 g of pure peroxyoctanoicacid. A 1:10 dilution with deionized water gave a 1000 ppm workingsolution of peroxyoctanoic acid. A 5 ppm use solution of peroxyoctanoicacid was obtained by diluting 1.25 ml of the working solution to 250 mlwith deionized water.

Mixtures of the various peroxyacids were prepared in a similar fashionby adding the appropriate amount of each peroxyacid working solution toa volumetric flask and diluting to 250 ml with deionized water. In allcases, the sample solutions were tested soon after dilution to assurethat no decomposition of the peroxyacids had occurred.

The microbiological testing followed the standard AOAC procedure, AOACOfficial Methods of Analysis, 15th Edition, 1990, Germicidal andDetergent Sanitizing Action of Disinfectants, with the addition ofMcIlvaine's citric acid-phosphate buffer to maintain the pH of thesanitizer solution at pH 4.5. Contact time was 30 seconds. Testing wasdone in duplicate with the following results as summarized in Table XI.

                  TABLE XI                                                        ______________________________________                                        COOPERATIVE INTERACTION OF PEROXYACIDS                                        C.sub.2     C.sub.5  C.sub.8  Log Reduction                                   Sample (POAA.sup.1)                                                                           (POGA.sup.2)                                                                           (POOA.sup.3)                                                                         S. aureus                                                                             E. coli                               ______________________________________                                        1      25 ppm   0        0      0, 0.2  0.5, 0.5                              2      50 ppm   0        0      1.6, 1.4                                                                              1.9, 2.5                              3      0        25 ppm   0      0,0     0.4, 0.4                              4      0        50 ppm   0      0.11 0.1                                                                              1.4, 1.2                              5      0        0        5 ppm  >6, 6.0 1.6, 1.6                              6      25 ppm   25 ppm   0      1.2, 1.2                                                                              2.7, 2.9                              7      25 ppm   50 ppm   0      2.1, 1.9                                                                              >7, >7                                8      0        25 ppm   5 ppm  >6, >6  5.0, >7                               9      0        50 ppm   5 ppm  >6, >6  >7, >7                                10     25 ppm   0        5 ppm  >6      >7                                    ______________________________________                                         .sup.1 POAA = Peroxyacetic Acid, a C.sub.2 acid                               .sup.2 POGA = Peroxyglutaric Acid, a C.sub.5 acid                             .sup.3 POOA = Peroxyoctanoic Acid, a C.sub.8 acid                        

The above data clearly shows a much greater than additive antimicrobialactivity (synergism) when the peroxyglutaric (C₅) acid was combined withperoxyoctanoic (C₈) acid (Samples 8 and 9). A similar but weaker effectwas obtained when peroxyacetic (C₂) acid was combined withperoxyglutaric acid (Samples 6 and 7).

It should be noted that S. aureus is very sensitive to peroxyoctanoicacid, thus it is difficult to use this organism to demonstrate asynergism between peroxyoctanoic acid and other peroxyacids. However, E.coli is not particularly sensitive to any of the above singleperoxyacids at the concentrations tested (see Samples 1-5), butcombinations of peroxyglutaric acid with either peroxyacetic acid orperoxyoctanoic acid were surprisingly active. The combination ofperoxyglutaric acid with peroxyoctanoic acid was particularly effective,and this combination displays a marked synergism (especially note thedata for E. coli for Samples 8 and 9 and compare with the additiveeffects of Samples 3 or 4 with Sample 5). Thus, a combination of thesetwo peroxyacids (C₅ and C₈) displays surprisingly effective bacterialkill against these representative gram positive and gram negativemicroorganisms at concentrations that provide real economic and safetybenefits.

EXAMPLE 16

Two formulas were prepared with the following ingredients as listed inTable XII.

                  TABLE XII                                                       ______________________________________                                        Ingredient   Formula 1 (wt-%)                                                                            Formula 2 (wt-%)                                   ______________________________________                                        H.sub.2 O.sub.2 (35%)                                                                      89            81                                                 Dequest 2010  1            1                                                  Glutaric Acid                                                                              10            10                                                 Octanoic Acid                                                                              --            3                                                  n-Octane Sulfonate                                                                         --            5                                                               100           100                                                ______________________________________                                    

Each of the above formulas was allowed to stand at room temperature andequilibriate for seven days and was then titrated for total peroxyacid(calculated as peroxyglutaric acid). Formula 1 contained 7.49%peroxyglutaric acid, while Formula 2 contained 7.78% peroxyacids(calculated as peroxyglutaric acid but really a mixture of POGA andPOOA).

The bacterial kill properties of the above two formulas were examinedusing E. coli as the test organism at room temperature in deionizedwater at 50 ppm total peroxyacid (as determined by titration of eachformula, followed by appropriate dilution). The results are summarizedin Table XIII below.

                  TABLE XIII                                                      ______________________________________                                        Bacterial Kill, E. coli, at 50 ppm Peroxyacid                                          Log Reduction                                                                 pH                                                                            2.2   4.0        6.0     8.0                                         ______________________________________                                        Formula 1  4.2     5.3        0.7   0.3                                       Formula 2  >6.9    >7.2       >7.2  3.2                                       ______________________________________                                    

Thus, 50 ppm of the peroxyacids in Formula 2 has a much more effectivekill than 50 ppm of peroxyglutaric acid alone in Formula 1.

The solubilizer present in Formula 2 does not contribute significantlyto bacterial kill. Thus, we have shown a simple way of enhancing thekill properties of peroxyglutaric acid. We merely formulate a productthat contains hydrogen peroxide, glutaric acid, an appropriate fattyacid, a stabilizer and a solubilizer (for the fatty acid). On standing,this mixture will form an equilibrium mixture of peroxyacids. Mixturesof appropriate peroxyacids will be synergistic and effective at lowconcentrations. Glutaric acid has a very low odor, and monocarboxylicacids of chain length of C₈ or greater, especially at these lowerconcentrations, are also of low odor. Thus, we can readily formulatesynergistic compositions hat possess acceptably low odor even in theconcentrated formula, but especially at use dilutions.

EXAMPLE 17

A mixture of short chain fatty acids commercially available from EmeryCorporation under the designation "EMERY 658" was employed in producinga sanitizing concentrate composition of the present invention. The"EMERY 658" acid is a mixture of caprylic acid (C₈) and capric acid(C₁₀). The perfatty acids were prepared by the method of Parker, et al.,J. Amer. Chem. Soc., 77, 4037 (1955) which is incorporated by reference.The perfatty acid component (also containing 34% acetic acid and 10%hydrogen peroxide) was combined with a pre-made solution of 10.42%peracetic acid, a separate amount of acetic acid, water, and ann-octanesulfonate hydrotrope coupler (NAS 8D). The final composition ofthis Example was as listed in Table XIV.

EXAMPLE 18

A second composition of the present invention was prepared as describedin Example 17, except that caprylic acid (C₈) and capric acid (C₁₀)replaced some of the perfatty acid of Example 17. The concentration ofperacetic acid was 5% while the concentration of perfatty acids wasreduced to 1.5% (see Table XIV).

EXAMPLE 19

The composition of Example 19 was prepared according to the procedure ofExample 17, except that no peracetic acid or hydrogen peroxide was addedto the composition. The acetic acid component was increased to 39 wt-%and the composition contained 5% perfatty acid (see Table XIV). Also, achelating agent (Dequest 2010) was added to the composition.

EXAMPLE 20

The composition of Example 20 was prepared the same as Example 19 exceptthat caprylic acid and capric acid were added to the composition inaddition to the percaprylic and percapric acid of Example 19. Thecomposition contained 3.5% fatty acid and 1.5% perfatty acid (see TableXIV).

EXAMPLE 21

Example 21 was prepared with only peracetic acid, acetic acid, hydrogenperoxide, and water. No perfatty acids or fatty acids were added to thecomposition of Example 21. The concentration of total peracid was about5% and the acetic acid concentration was about 39% (see Table XIV).

EXAMPLE 22

Example 22 was prepared the same as Example 20 except that no peracidswere employed, only a mixture of fatty acids and acetic acid was used,along with water, NAS 8D, and Dequest 2010. The composition contained 5%fatty acid (see Table XIV).

                  TABLE XIV                                                       ______________________________________                                               Wt-% of Ingredients                                                    Ingredient                                                                             Ex. 17  Ex. 18  Ex. 19                                                                              Ex. 20                                                                              Ex. 21                                                                              Ex. 22                             ______________________________________                                        Peracetic                                                                              50      50      --    --    50    --                                 Acid                                                                          (10.42% solu-                                                                 tion, 34%                                                                     acetic acid,                                                                  10% H.sub.2 O.sub.2)                                                          Acetic Acid                                                                            22      22      39    39    22    39                                 Percaprylic                                                                            3.75    1.125   3.75  1.125 --    --                                 Acid (C.sub.8)                                                                Percapric                                                                              1.25    0.375   1.25  0.375 --    --                                 Acid (C.sub.10)                                                               Caprylic --      2.625   --    2.625 --    3.75                               Acid (C.sub.8)                                                                Capric   --      0.875   --    0.875 --    1.25                               Acid (C.sub.10)                                                               NAS 8D   10      10      10    10    --    10                                 Water    13      13      45    45    28    45                                 Dequest 2010                                                                           --      --      1     1     --    1                                  ______________________________________                                    

Antimicrobial Efficacy of Examples 17-22

The compositions prepared according to Examples 17-22 were-tested fortheir antimicrobial efficacy using the testing procedure of the standardA.O.A.C. sanitizing test. All of the samples tested of Examples 17-22were made about 1 hour prior to testing. The bacteria used in the testprocedure were S. aureus and E. coli. Distilled water was used to dilutethe concentrate compositions of Examples 17-22 and the composition wasemployed at room temperature. The following neutralizers were employedin the test: 0.1% thiosulfate, peptone, 0.5% K₂ HPO₄, 0.025% catalasefor peracetic acid; chambers for fatty acid; 0.1% thiosulfate, peptone,0.025% catalase for peracetic acid/fatty acid (perfatty acid).

The antimicrobial activity of Examples 17-22 are summarized in Table XV.Examples 17 and 18 were tested using four samples (a,b,c,d) and Examples19-22 were tested using two samples (a,b). As can be seen in Table XV,Examples 17-20 exhibited excellent kill (>log 6) of both S. aureus andE. coli at 50 ppm of peracid. Examples 21 and 22 (containing no perfattyacids) exhibited little or no activity. More specifically, Example 17was tested at 1,000 and 500 ppm total product (50 and 25 ppm of bothperoxyacetic acid and perfatty acid). At these low concentrations, theperacid combination gave a 6-7 log reduction in the bacterial count.Example 18 was tested at 1,000 and 500 ppm total product, and also had a6-7 log reduction in the bacterial count. At the 500 ppm productconcentration the product corresponds to 25 ppm of peroxyacetic acid and7.5 ppm of perfatty acids. Example 19, at 1,000 ppm of total product (50ppm of perfatty acid), completely killed all bacteria (greater than 7log. reduction). Example 20 also resulted i a complete kill using 1,000ppm of total product (15 ppm perfatty acid). Example 21 contained noperfatty acid (only 50 ppm of peroxyacetic acid) and showed no activityagainst S. aureus and poor activity against E. coli. This is due to thefact that peroxyacetic acid is generally not effective at this level,and is generally used at concentrations greater than 100 ppm. Example22, containing 5% fatty acid (30 ppm) and no perfatty acid at 1,000 ppmtotal product showed no activity toward either organism.

                                      TABLE XV                                    __________________________________________________________________________           Test Product                                                                          POAA.sup.1 /POFA.sup.2 /FA.sup.3                                      Concentration                                                                         Concentration Log.sub.10 Kill                                  Ex.                                                                              Sample                                                                            (ppm)   (ppm)      pH S. aureus                                                                          E. coli                                     __________________________________________________________________________    17 a   1000    50/50/0    3.5                                                                              6.13 >7.30                                          b   1000    50/50/0    3.5                                                                              6.52 7.30                                           c    500    25/25/0    3.68                                                                             6.63 7.00                                           d    500    25/25/0    3.68                                                                             6.78 7.30                                        18 a   1000    50/15/35   3.52                                                                             7.18 7.30                                           b   1000    50115/35   3.52                                                                             6.63 6.90                                           c    500    25/7.5/17.5                                                                              3.68                                                                             6.70 6.76                                           d    500    25/7.5/17.5                                                                              3.68                                                                             7.18 7.00                                        19 a   1000    0/50/0     3.5                                                                              >7.18                                                                              >7.30                                          b   1000    0/50/0     3.5                                                                              >7.18                                                                              >7.30                                       20 a   1000    0/15/35    3.5                                                                              >7.18                                                                              >7.30                                          b   1000    0/15 35    3.5                                                                              >7.18                                                                              >7.30                                       21 a   1000    50/0/0     3.49                                                                             .sup. NMA.sup.4                                                                    3.48                                           b   1000    50/0/0     3.49                                                                             NMA  3.80                                        22 a   1000    0/0/30     3.46                                                                             NMA  NMA                                            b   1000    0/0/30     3.46                                                                             NMA  NMA                                         __________________________________________________________________________     .sup.1 POAA = Peroxyacetic Acid                                               .sup.2 POFA = Peroxyfatty Acid                                                .sup.3 FA = Fatty Acid                                                        .sup.4 NMA = No measurable activity.                                     

EXAMPLE 23-26

Examples 23-26 were prepared by substantially the same procedure as theprevious Examples, except that hydrogen peroxide (H₂ O₂) was mixed withacetic acid and C₈₋₁₀ fatty acids (Emery 658) to make the peracids ofthe composition. Table XVI summarizes the components and amounts of thevarious compositions of Examples 23-26 which were made.

                  TABLE XVI                                                       ______________________________________                                        Peracid Test Formulations                                                     Ingredient  Ex. 23  Ex. 24    Ex. 25                                                                              Ex. 26                                    ______________________________________                                        Acetic Acid 44      39        34    49                                        H.sub.2 O.sub.2 (35%)                                                                     40      40        40    40                                        Dequest 2010                                                                               1       1         1     1                                        NAS 8D      10      10        10    10                                        Emery 658    5      10        15    --                                        ______________________________________                                    

Peracid Stability, Cidal Activity of Examples 23-26

Each of Examples 23-26 were tested for peracid stability and cidalactivity using the A.O.A.C. sanitizing test against S. aureus and E.coli at room temperature with the formulations diluted in distilledwater. Tables XVII-XX show the cidal activity of each formulation.Generally all of the formulations reached maximum peracid formationwithin about 12 days. All of the formulations obtained about 12.5%peracid except Example 25 (15% fatty acid) which obtained about 11.5%peracid.

Table XVII summarizes the cidal activity of Example 23 in which thecomposition was measured for cidal activity on the first day up to day33. At 250 ppm of total product, there were about 4-5 ppm of perfattyacid and about 20 ppm of peracetic acid as determined by carbon 13 NMRspectroscopy of the concentrate. The results are summarized in TableXVII.

                  TABLE XVII                                                      ______________________________________                                        Peracid Stability,                                                            Cidal Activity of Example 23                                                  Peracid    Test.sup.(a)                                                                              Test    Ave. Log Reduction                             Day  Percent   Concentration                                                                             pH    S. aureus                                                                            E. coli                               ______________________________________                                        1    4.28      250 ppm     3.92  6.28   NMA.sup.(b)                           6    11.00     250 ppm     3.91  >7.38  >7.18                                 8    11.08     250 ppm     3.86  >7.11  >7.12                                 12   12.43     250 ppm     3.83  >7.18  6.96                                  15   12.74     250 ppm     3.88  6.95   --                                    33   10.18     250 ppm     3.83  5.18   6.34                                  ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

The cidal activity of Example 24 is summarized in Table XVIII below. Theperacetic acid concentration at 250 ppm of product was about 20-21 ppmand the concentration of perfatty acid was about 11 ppm. Theconcentration of peracetic acid at 50 ppm of product was about 4 ppm andthe concentration of perfatty acid was about 2 ppm.

                  TABLE XVIII                                                     ______________________________________                                        Peracid Stability,                                                            Cidal Activity of Example 24                                                  Peracid    Test.sup.(a)                                                                              Test    Ave. Log Reduction                             Day  Percent   Concentration                                                                             pH    S. aureus                                                                            E. coli                               ______________________________________                                        1    4.88      250 ppm     3.95  >7.60  NMA.sup.(b)                           2    10.62     250 ppm     3.92  >7.38  >7.18                                 8    11.61     250 ppm     3.98  >7.11  >7.12                                 12   12.47     250 ppm     3.91  >7.18  >7.23                                 15   12.00     250 ppm     3.95  6.95   --                                                   120 ppm     4.18  >7.13  --                                                    50 ppm     4.41  6.39   --                                    33   10.49     250 ppm     3.85  5.20   6.22                                  ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

The cidal activity of Example 25 is summarized in Table XIX below. At250 ppm of product the peracetic acid concentration was about 19 ppm andthe perfatty acid concentration was about 14 ppm.

                  TABLE XIX                                                       ______________________________________                                        Peracid Stability,                                                            Cidal Activity of Example 25                                                  Peracid    Test.sup.(a)                                                                              Test    Ave. Log Reduction                             Day  Percent   Concentration                                                                             pH    S. aureus                                                                            E. coli                               ______________________________________                                        1    4.84      250 ppm     3.90  >7.60  NMA.sup.(b)                                                                   4.04                                  6    9.81      250 ppm     3.96  >7.38  >7.18                                 8    10.99     250 ppm     3.96  >7.11  >7.12                                 12   11.47     250 ppm     3.94  >7.18  >7.23                                 15   11.48     250 ppm     3.96  6.83   --                                    33   10.49     250 ppm     3.95  5.25   6.53                                  ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

The cidal activity of Example 26 is summarized in Table XX below. At 250ppm of product there was about 27 ppm of peracetic acid. At 1000 ppm ofproduct there was about 108 ppm of peracetic acid. No fatty acid wasemployed in the composition of Example 26.

                  TABLE XX                                                        ______________________________________                                        Cidal Activity of Example 26                                                  Peracid    Test.sup.(a)                                                                              Test    Ave. Log Reduction                             Day  Percent   Concentration                                                                             pH    S. aureus                                                                            E. coli                               ______________________________________                                        5    10.95      250 ppm    3.90  NMA.sup.(b)                                                                          NMA                                   7    12.03     1000 ppm    3.50  4.60   >7.12                                 11   12.44     1000 ppm    3.49  6.38   6.64                                  14   12.53     1000 ppm    3.50  4.17   --                                    32   10.77     1000 ppm    3.45  4.77   6.44                                  ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

When comparing the formulations containing fatty acid (Tables XVII-XIX),poor activity was measured against E. coli one day after beingformulated. Since the total peracid values were low, more fatty acid waspresent and gram negative bacteria tend to be less sensitive than grampositive bacteria to the C₈ -C₁₀ fatty acids. However, as more peraciddeveloped over the days indicated, increased cidal activity against E.coli was observed. Table XX indicates that to obtain acceptable activity(greater than or equal to 5 log reduction) using only peracetic acid,the peracetic acid must be tested over 100 ppm active. Secondly, thisoxidizing compound is more effective against E. coli than S. aureus.

Generally all the formulations containing fatty acid remain stable afterabout 1 month. This was confirmed by repeated testing over time at 250ppm total product for each formulation in which greater than 5 logreductions were measured against S. aureus and E. coli.

EXAMPLE 27-32

The cidal activity of a two-component system containing both peraceticacid and fatty acid was investigated using the A.O.A.C. sanitizing test.Table XXI shows the product formulations examined. The test samplesinclude controls showing cidal activity of NAS 8D as well as fatty acidkill against S. aureus. All the samples were tested in distilled water.

                  TABLE XXI                                                       ______________________________________                                               Wt-% Ingredient                                                        Ingredient                                                                             Ex. 27  Ex. 28  Ex. 29                                                                              Ex. 30                                                                              Ex. 31                                                                              Ex. 32                             ______________________________________                                        Base 1.sup.(a)                                                                         80      80      80    80    --    --                                 Base 2.sup.(b)                                                                         --      --      --    --    80    80                                 NAS 8D   10      --      10    10    10    10                                 Octanoic --      --      10    --    --    10                                 Acid                                                                          Emery 658                                                                              --      --      --    10    10    --                                 H.sub.2 O                                                                              10      20      --    --    --    --                                 ______________________________________                                         .sup.(a) H.sub.2 O.sub.2, 35%; acetic acid, 35%; Dequest 2010, 1%; H.sub.     PO.sub.4 (85%), 29%.                                                          .sup.(b) Acetic acid, 35%; Dequest 2010, 1%; H.sub.3 PO.sub.4 (85%), 29%;     H.sub.2 O, 35%.                                                          

Table XXII shows the activity measurement of each of Examples 27-32 atvarious test concentrations. When testing the peracetic acid formulationof Examples 27 and 28 (having no fatty acid), biocidal activity occurredonly at 100 ppm or greater. Cidal activity (greater than 4 logreduction) was measured at a minimal concentration of 10 ppm peracidwith fatty acid in the system (Example 29). At 10 ppm peracid, thecomposition containing Emery 658 (Example 30) had better activity thanthe system containing only C₈ (octanoic) fatty acid (Example 29). In thefatty acid controls having no oxidant (Examples 31 and 32), the Emery658 had more cidal activity than the C₈ fatty acid. At total producttest concentrations equivalent to 10 or 25 ppm peracid, the fatty acidin the system of Example 31 did not have significant cidal activity.Example 32 did not have significant cidal activity at any testconcentration.

                  TABLE XXII                                                      ______________________________________                                        Peracid Cidal Activity Against S. aureus                                             Peracid   Concentration                                                                              Test  Log.sup.(a)                               Example                                                                              (%)       (ppm Peracid)                                                                              pH    Reduction                                 ______________________________________                                        27     7.02      50           2.79  NMA.sup.(b)                                                100          2.54  5.45                                                       150          2.41  >7.70                                     28     6.25      50           2.76  NMA                                                        100          2.52  4.51                                                       150          2.40  5.84                                      29     9.32      10           3.52  4.22                                                       25           3.16  >7.70                                                      50           2.90  >7.70                                     30     9.73      10           3.50  6.82                                                       25           3.19  7.55                                                       50           2.88  >7.70                                     31     --        --.sup.(c)   3.53  0.70                                                       --.sup.(c-1) 3.18  1.04                                                       --.sup.(c-2) 2.88  4.07                                      32     --        --.sup.(d)   3.51  0.93                                                       --.sup.(d-1) --    0.66                                                       --.sup.(d-2) --    0.97                                      ______________________________________                                         .sup.(a) Average of duplicate testing.                                        .sup.(b) No measurable activity.                                              .sup.(c) Same total product concentration as Example 30 @ 10 ppm peracid      (about 100 ppm product).                                                      .sup.(c1) Same total product concentration as Example 30 @ 25 ppm peracid     (about 250 ppm product).                                                      .sup.(c2) Same total product concentration as Example 30 @ 50 ppm peracid     (about 500 ppm product).                                                      .sup.(d) Same total product concentration as Example 29 @ 10 ppm peracid      (about 100 ppm product).                                                      .sup.(d1) Same total product concentration as Example 29 @ 25 ppm peracid     (about 250 ppm product).                                                      .sup.(d2) Same total product concentration as Example 29 @ 50 ppm peracid     (about 500 ppm product).                                                 

The cidal activity of a peracetic acid/fatty acid system was measuredcomparing freshly made formulations to month-old formulations ofExamples 30 and 31. These formulations are shown in Table XXIII whichcompares the titration values of month-old formulations to the samefreshly prepared. Table XXIV shows the cidal activity of month-old andfresh formulations of Examples 29 and 30.

                  TABLE XXIII                                                     ______________________________________                                        Peracid Titration Values                                                               Ex. 29  Ex. 30     Ex. 29  Ex. 30                                    ______________________________________                                        Date formulated                                                                          Month-Old Month-Old  Fresh Fresh                                   % H.sub.2 O.sub.2                                                                        2.15      2.07       1.99  1.99                                    % Peracid  5.37      5.35       4.85  4.86                                    % Total O.sub.2                                                                          2.14      2.10       1.96  1.96                                    ______________________________________                                    

                  TABLE XXIV                                                      ______________________________________                                        Peracid Cidal Activity Against S. aureus                                               Peracid  Test Concentration                                                                          Test Log.sup.(a)                              Example  (%)      (ppm Peracid) pH   Reduction                                ______________________________________                                        29       5.37     10            3.46 NMA.sup.(b)                              (Month-Old)       25            3.07 >7.48                                    29       4.85     10            3.34 5.07                                     (Fresh)           25            2.97 7.30                                     30       5.35     10            3.52 5.29                                     (Month-Old)       25            3.04 7.24                                     30       4.86     10            3.42 NMA.sup.(c) /                            (Fresh)           25            2.99 7.48                                     ______________________________________                                         .sup.(a) Average of duplicate testing.                                        .sup.(b) No measurable activity (3.68 log reduction).                         .sup.(c) Duplicate testing in which only one sample exhibited cidal           activity.                                                                

As can be seen from Table XXIV, cidal activity in the peraceticacid/fatty acid system occurs at test concentrations as low as 10 or 25ppm peracid. Mixed results occurred at 10 ppm peracid between themonth-old and fresh formulations of Examples 29 and 30, however,increasing the concentration to 25 ppm resulted in a uniform killactivity (>7 log reduction).

An additional test was run to determine how quickly compounds exhibitingcidal activity are formed upon adding fatty acid to a peracetic acidsystem. Examples 27, 30 and were tested. Examples 27 and 30 wereformulated the day before testing and were day-old samples. Another testsample of Example 30 was formulated immediately prior to testing.Example 31 containing Base 2 (no H₂ O₂) was used to show cidal activityfrom the fatty acid at low test concentrations. Table XXV shows thecidal activity of each Example in distilled water against S. aureus.

                  TABLE XXV                                                       ______________________________________                                        Cidal Activity Against S. aureus                                                                ppm        Test  Log.sup.(a)                                Example   Age     Peracid    pH    Reduction                                  ______________________________________                                        27        1 day   50         2.94    NMA.sup.(b)                                                100        2.71  6.60                                       30        1 day   10         3.68  7.02                                                         25         3.35  >7.20                                      30        fresh   10         3.76  NMA                                                          25         3.32  NMA                                        31        22 days --.sup.(c) 3.74  NMA                                                          --.sup.(d) --    NMA                                        ______________________________________                                         .sup.(a) Average of duplicate testing.                                        .sup.(b) No measurable activity.                                              .sup.(c) Equivalent total product concentration as Example 30 (day old) @     10 ppm peracid.                                                               .sup.(d) Equivalent total product concentration as Example 30 (day old) @     25 ppm peracid.                                                          

The data from Table XXV suggests that the formulation of compoundscontaining cidal activity when adding fatty acid to a peracetic acidsystem is not immediate, but does occur within a day. The formulation ofcompounds exhibiting cidal activity occurred within a day after addingfatty acid to the peracetic acid system as in Example 30 with cidalactivity occurring at a concentration as low as 10 ppm peracid. Thus,the cidal activity is not due to the mere combination of fatty acid andperoxyacetic acid, but he fatty acid must be converted to the perfattyacid before substantially enhanced cidal activity occurs.

The foregoing discussion and Examples are illustrative of the invention.However, since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

We claim:
 1. A peroxyacid antimicrobial concentrate compositionconsisting essentially of:(a) an effective biocidal amount ofperoxyglutaric acid; and (b) an effective biocidal amount of aperoxyacid selected from the group consisting of an aliphatic C₆ -C₁₈aliphatic peroxyacid, and mixtures thereof;wherein the concentratecomposition is capable of being diluted with a major proportion of waterto form an antimicrobial use solution that can achieve a 5 log reductionin a microbial population at a pH in the range of about 2 to
 8. 2. Theconcentrate composition of claim 1 which consists of about 1 to 25 wt-%of said peroxyglutaric acid.
 3. The concentrate composition of claim 1which consists of about 0.01 to 20 wt-% of said peroxyacid of (b). 4.The concentrate composition of claim 1 wherein said C₆ -C₁₈ isperoxyacid is selected from the group consisting of an aliphaticmonoperoxy carboxylic acid or a diperoxydicarboxylic acid.
 5. Theconcentrate composition of claim 4 wherein said C₆ -C₁₈ peroxyacid isselected from the group consisting of peroxyoctanoic acid,peroxydecanoic acid, monoperoxy- or diperoxyadipic acid, monoperoxy- ordiperoxysebacic acid, and mixtures thereof.
 6. The concentratecomposition of claim 1 wherein the weight ratio of said C₅ peroxyacid tosaid peroxyacid of (b) is about 20:1 to 1:10 and the microbialpopulation is reduced in less than 120 seconds.
 7. The concentratecomposition of claim 1 further consisting of an effective amount of ahydrotrope coupling agent capable of solubilizing said C₆ -C₁₈peroxyacid in the concentrate and when the concentrate is diluted withwater.
 8. The concentrate composition of claim 7 wherein saidconcentrate is about 0.1 to 30 wt-% of said hydrotrope coupling agent.9. The concentrate composition of claim 8 wherein said hydrotrope isselected from the group consisting of n-octanesulfonate, a xylenesulfonate, a naphthalene sulfonate, and mixtures thereof.
 10. Theconcentration composition of claim 1 further consisting of a carboxylicacid selected from the group consisting of glutaric acid an aliphatic C₆-C₁₈ carboxylic acid, and mixtures thereof.
 11. The concentratecomposition of claim 10 wherein said C₆ -C₁₈ carboxylic acid is selectedfrom the group consisting of octanoic acid, decanoic acid, adipic acid,sebacic acid, and mixtures thereof.
 12. The concentrate composition ofclaim 1 further consisting of hydrogen peroxide.
 13. The concentratecomposition of claim 12 wherein said concentrate is about 1 to 50 wt-%of said hydrogen peroxide.
 14. The concentrate composition of claim 1wherein said composition can form a use solution having a pH of about 3to 7 and the microbial population is reduced in less than 30 seconds.15. A peroxyacid antimicrobial concentrate composition consistingessentially of:(a) about to 1 to 25 wt-% of peroxyglutaric acid; (b)about 0.01 to 10 wt-% of a peroxyacid of the structure R₁ --CO₃ H,wherein R₁ comprises an aliphatic hydrocarbon chain having about 5 to 17carbon atoms; (c) about 0.1 to 30 wt-% of a hydrotrope coupling agentcapable of solubilizing said peroxyacid of (b) in the concentrate andwhen the concentrate is diluted with water; and (d) about 1 to 50 wt-%of hydrogen peroxide; wherein the concentrate composition is capable ofbeing diluted with a major proportion of water to form an antimicrobialsanitizing use solution that can achieve a 5 log reduction in amicrobial population at a pH in the range of about 3 to
 7. 16. Theconcentrate composition of claim 15 wherein said peroxyacid of (b) is aperoxyfatty acid having about 8 to 12 carbon atoms per molecule.
 17. Theconcentrate composition of claim 16 wherein said peroxyfatty acid isperoxyoctanoic acid, peroxydecanoic acid, or mixtures thereof.
 18. Theconcentrate composition of claim 16 wherein the weight ratio of saidperoxyglutaric acid to said peroxyfatty acid is about 20:1 to 2:1. 19.The concentrate composition of claim 15 wherein said hydrotrope isn-octanesulfonate.
 20. The concentrate composition of claim 16 furtherconsisting of about 5 to 50 wt-% of a carboxylic acid selected from thegroup consisting of a fatty acid, glutaric acid, and mixtures thereof.21. The concentrate composition of claim 20 wherein said fatty acid isoctanoic acid, decanoic acid, or mixtures thereof.